Metric design - will it be possible to replace the 1/4" threaded rod with a 8mm one?

The red fully-printed design looks great! I love it and am grateful it is to be released into open source. I am planing to make one once the design is published, and did contribute to the online campaign.

My question is - how easy will it be to replace all the imperial measurements specific elements with metric ones? I had a glance at the BOM and there is 1/4" threaded rod. I want to replace it with a proper lead-screw, but 1/4" - 6,35mm is not easily sourced where I live. 8mm is what's on the market.

Is it parametric in the Blender design?

mfeherpataky Wrote:
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> The red fully-printed design looks great! I love
> it and am grateful it is to be released into open
> source. I am planing to make one once the design
> is published, and did contribute to the online
> campaign.
>
> My question is - how easy will it be to replace
> all the imperial measurements specific elements
> with metric ones?

Most of it should be easy with the exception of the 5/16" smooth rods. They have to fit through the 608 bearings which are 8mm bore and true 8mm smooth rod would require a press fit. The rods I am supplying in the kits are high tolerance 8mm +/- 0.013mm and 5/16" (7.9375mm) +/- 0.013mm . But as many people mentioned in the announcement thread a lot of what is sold as 8mm is actually small enough to fit through the 608 bearings. The rods in the BOM marked 8mm should really be high tolerance to eliminate any play in the LM8uu's.

I had a glance at the BOM and
> there is 1/4" threaded rod. I want to replace it
> with a proper lead-screw, but 1/4" - 6,35mm is not
> easily sourced where I live. 8mm is what's on the
> market.

8mm would be to thick and make assembly really hard, the machine has very little clearance around 80% of the moving parts. If using threaded rod as designed I would go with 6mm or 5mm. Also it's important to use stainless steel threaded rod because the threads are usually more accurate (from my tests the differences are remarkable).

>
> Is it parametric in the Blender design?

Yes, most of the boolean functions have been left un-applied to allow you to move, resize, replace, reshape them and then just export the new part. Some of the parts are currently grouped which will throw some people off that are new to Blender but they are really easy to separate. For example: the nut traps on the printed case are all grouped together right now to cut down on the number of individual parts. To separate them you select them, press "tab" to enter edit mode, press "p" and select "individual parts", press "tab" again to exit edit mode and now you have all the nut traps separated. To re-group them you select them all while holding shift and then press "ctrl j" to join them. Really simple once you get used to my work flow but different from CAD software.

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Thank you for a great and speedy response!
It also explained other thing in BOM - the difference in between 5/16" and 8mm drill rods .

On the leads-crew subject - do you think it would provide noticeable benefits vs a threaded rod in a machine this size? How the size translates into reliability of the singular threaded rod for the z-axis? I jumped, perhaps unnecessary, for a lead-screw solution as the Tantillus design is meant for small object with possible micons layer height.

mfeherpataky Wrote:
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> On the leads-crew subject - do you think it would
> provide noticeable benefits vs a threaded rod in a
> machine this size?

If you like to use Z-lift on travel moves I could see how using a ball screw would eliminate the minor backlash you find on threaded rod drive. But on uni-directional Z moves you would most likely not see any improvement.

How the size translates into
> reliability of the singular threaded rod for the
> z-axis?

I use small diameter S/S threaded rod for lead screws on all my machines, including my Prusa and RepStrap and they provide more reliable layer alignment than 8mm.

I jumped, perhaps unnecessary, for a
> lead-screw solution as the Tantillus design is
> meant for small object with possible micons layer
> height.

Its not necessarily for small objects but it does seem to do them better than most machines.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver